Variable Speed Compressors for Improved Energy Efficiency

Energy efficiency is one of the most important factors all businesses are concerned with. The more efficient your air system, the lower your energy consumption and the cheaper your energy bill!

A vast amount of the energy that is lost in a factory or plant is due to wasted energy in an air compressor installation. This can have a huge effect on energy costs, raising your bills and making your cost of ownership high. Various technologies have been developed to ensure that compressed air systems are performing as efficiently as possible, one such technology is variable speed drives (VSD).

Traditional air compressors are fixed speed, meaning they run at a constant and consistent speed. This produces a fixed amount of compressed air per minute. There are many benefits to fixed speed compressor technology if your compressed air demand is constant and unchanging. However, this isn’t always the case. As fixed speed compressors are always operating at full-throttle, if all of the output is not required then energy is being wasted.

Furthermore, fixed speed compressors run unloaded as the stress of an engine start-up would put pressure on the motor. This can be a waste of energy as the machine is running without producing any compressed air. Variable speed compressors avoid this issue by matching the output with the demand created. By simply producing the exact amount of air being used by the downstream equipment, variable speed compressors help to improve plant efficiency.

Watch this video to see how a fixed speed compressor can be sequenced with a variable speed machine to precisely match output with network demand to save energy.

Many air compressor installations will benefit from the efficiency variable speed drive technology provides. Whether you are in the food and beverage industry, automotive, medical industry or even manufacturing, there will be times when your demand for compressed air will vary.

A combination of both variable and fixed speed compressors is thought to be the most cost-effective and advantageous set-up, resulting in the most energy saved and demands met.

Thermocompressor Installation & Troubleshooting

A thermocompressor is a steam control device that uses high-pressure steam (motive steam) to induce flow from a lower pressure steam source (suction steam) and discharge the mixture at an intermediate pressure. The high pressure is used to create a high velocity jet that mixes with and accelerates the suction steam. The velocity of the mixture is exchanged for increased pressure in the diffuser. A Kadant Johnson thermocompressor is shown above.

Installation
Thermocompressors can be installed in any orientation, but directing the discharge horizontally or downward is preferred. A thermocompressor should be independently supported. Using the unit to support piping can impose excessive loads and cause bending and misalignment.

Suction and Discharge Piping
Suction piping must be independently supported. It should be full size to match the suction connection on the thermocompressor. Avoid filters, valves and other fittings that cause pressure loss in the suction line that were not considered in the original design specification. Use low-pressure drop non-return valves and full bore ball or gate type isolation valves in all locations to minimize pressure losses. Avoid low points or loops that might accumulate condensate. A steam pressure gauge with an isolation valve should be located as close to the low-pressure inlet as possible.

Discharge piping should be the same diameter as the discharge connection on the thermocompressor. Discharge piping must be independently supported. Care should be taken to avoid placing restrictions or undue obstructions that will increase the discharge pressure above the design point. A minimum length of 10 pipe diameters is recommended before an elbow to Tee. A steam pressure gauge with an isolation valve should be located as close to the discharge connection as possible.

Motive Steam
The line size should be determined based on the maximum design flow for the thermocompressor. Dry steam is a basic requirement for good performance and wet steam is extremely detrimental to both the performance and the parts of a thermocompressor. Motive pipe runs longer than 10 feet and should have a drip leg and trap to remove condensate from the piping before the motive steam enters the thermocompressor. High-flow losses in the supply lines should be avoided. As the motive pressure falls, the amount of steam required increases. A steam pressure gauge with an isolation valve should be located as close to the motive connection as possible.

Troubleshooting
A thermocompressor in the fully open or closed position during run conditions is usually a problem. Accuracy of the instrumentation and controls should be verified.

Substandard performance can usually be traced to either external or internal causes. Substandard performance can also be classified as either sudden or gradual. A gradual deterioration in performance, usually a loss of recompression, invariably suggests either erosion or corrosion, whereas a sudden loss of compression will usually suggest an external cause.

Since the external causes of trouble are usually easier to check, they should be investigated first.

When a fault is investigated, it is prudent to treat as suspect all the gauges fitted, especially Bourdon Tube type dial gauges. These gauges should, whenever it is possible, be recalibrated.